<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    function t1(a) {
        a += 10;
    }
    let a = 10;
    t1(a);
    console.log(a);

    function t2(obj) {
        obj.a += 10;
    }
    let obj = {a: 10};
    t2(obj);
    console.log(obj);
</script>
</body>
</html>